1. Field of the Invention
The invention relates broadly to the field of leveling devices used in, by way of example only, the construction industry. More particularly, the present invention relates to an improvement in the assembly of leveling devices that allows for precise adjustment or calibration of the leveling device, using economical manufacturing methods.
2. Description of the Related Art
In construction leveling devices, as well as other leveling devices, a small plastic or glass bubble vial is often used for a direct indication of level. The vial is mounted in the leveling device, such as a rail or other piece of equipment. A user identifies a level line by manipulating the leveling device until a small bubble in the vial is centered between two marks. Bubble vials have a range of features including specific sensitivity and accuracy. Multiple vials may be used to indicate level in multiple planes or particular set angles, such as 45 degrees.
In the manufacture and assembly of bubble vial leveling devices, the bubble vial is precisely aligned with respect to a gauging surface, to ensure accuracy of the device. Manufacturers typically employ one of three approaches for aligning bubble vials: (a) press fitting, (b) fixture positioning and gluing, or (c) providing for user adjustment.
In press fitting, manufacturers press fit plastic vials into a drilled or reamed hole. The hole is precisely bored with respect to the gauging surface, and does not allow for subsequent adjustment of the vial""s angle. In some instances, manufacturers use epoxy or glue to secure the vial""s fit.
In fixture positioning, manufacturers employ a mounting fixture to position a bubble vial in a bored holding cavity. In this approach, the holding cavity is less precisely bored than in press fitting. Once the vial is correctly positioned, the manufacturer secures the vial with glue or epoxy and removes the fixture.
As a third approach, manufacturers may fix the vial in a separate holder, such as a die-cast aluminum tray. The holder is then fixed with screws and springs. This allows users to adjust or calibrate the vial. If adjustment is desired in two planes, then a more complex holder is needed. The disadvantage of this method of creating adjustable vials is its extra cost of manufacturing, size, and complexity.
Alternatively, manufacturers may mount a vial in a machined hole having an oval slot on each end with counter-locking screws mounted on axes perpendicular to each other. This allows independent calibration in two planes. This arrangement, however, is difficult to machine in the practical configurations of a leveling device""s rail.
The invention described herein relates to a leveling device having an adjustable level indicator. Embodiments of the present invention provide for economical manufacture of adjustable levels by allowing a vial, or other level indicator, to be fitted into a loose extruded or imprecisely bored hole. The vial, or other level indicator, is then calibrated or adjusted to ensure operational accuracy.
One embodiment of the present invention includes a spring structure for securing a level indicator and a screw for adjusting the indicator""s position. The spring structure is mounted in a cavity in a leveling device. The spring structure includes two flexible elongated members that are deflected by the cavity""s walls. The elongated members place a resultant force on the level indicator to secure the indicator""s position in the cavity.
The screw extends into the cavity to apply an adjustment force to the level indicator. The adjustment force directs the level indicator to a position that results in a level indication when the leveling device is placed on a gauging surface. In one embodiment, the adjustment force is applied to align the level indicator""s centerline with the cavity""s centerline. The use of the spring structure and screw avoids the need to precisely extrude the cavity for holding the level indicator.
In one embodiment, multiple combinations of a spring structure and screw are employed to provide for adjustments in multiple planes. A first spring structure and screw secure a first end of a bubble vial and a second spring structure and screw secure a second end of the bubble vial. In one such embodiment, the first spring structure and second spring structure are positioned perpendicular to each other within the leveling device bore. This provides for the level indicator to be adjusted in two independent orthogonal planesxe2x80x94allowing precise calibration and operational accuracy of the leveling device with regard to all sides of the rail.
These and other objects and advantages of the present invention will appear more clearly from the following description in which the preferred embodiment of the invention has been set forth in conjunction with the drawings.